Wednesday, July 18, 2012

Severe Thunderstorm Watch Until 9 PM

Severe Thunderstorm Watches are still out until 9 PM for much of the Mid Atlantic and Southern New England, including New York City and Philadelphia.  Locally, a line of thunderstorms is approaching the region from the west, with numerous severe thunderstorm warnings out as the line approaches.  This line is working into upper 90's and near 100 degree heat, plus dew points in the lower and middle 70's, providing a perfect mix of ingredients to lead to atmospheric mayhem.

As of 4 PM, the line is located roughly from just south of Boston through the northern suburbs of New York back southwest into Lancaster County, with scattered storms firing out in Central and North Jersey.  The line is moving east and is producing heavy rain, gusty winds, and some hail.  Locally, the line of storms is a bit broken so some locations will get hit worse than others as this line moves in (see the radar below).  Note that these storms are "pulse" storms -- meaning that they can intensify and weaken relatively quickly despite travelling within a line.  Conditions can and have changed with the storms over the past couple of hours -- some spots that would be in line for a pummelling see the storm weaken as it moves in and others get a stronger storm than what the radar was showing 15, 20 minutes prior.

Timing-wise, this looks to move into Philadelphia after 5 PM, South Jersey just after that.  We'll continue to update as needed through the evening as we're able to.

Update, 6 PM:  The line of storms fizzled out as it approached the city from the west, with the brunt of activity now north through northeast of the city.  This line did impact more heavily to our north, with hail and gusty winds reported in a number of places through the Lehigh Valley, Berks County, and Bucks County over the past few hours.   Two other strong cells are to our southwest, one will pass to the north of Smyrna, DE, and the other will approach Dover, DE over the next couple of hours as they move east-northeast.  Those will work through South Jersey.  As for Philadelphia, a stray thunderstorm can't be ruled out over the next several hours as there are more thunderstorms back across Central PA moving southeast and east.

More:  Current Weather Page